Power pulses are utilized in many different types of applications. In many cases, there is a request for pulses having very high momentary power. Typical application areas range from radar systems, particle accelerators, sterilization equipment to high-energy lasers. Common for many such systems is that they require power pulse trains with very high momentary voltage and/or current.
A common approach for supplying such power pulses is to use different kinds of power modulators utilizing energy storage at moderate voltages and transforming short voltage pulses to higher voltages. There are numerous designs of such systems during the last century. Successful such systems in a more recent time are systems as disclosed in the U.S. Pat. Nos. 5,905,646 and 6,741,484, generally known as LCW systems. In these systems, a number of pulse generating modules are connected in parallel to a set of common primary windings of a transformer which have both terminals in common. By controlling the turning-on of the discharge of these pulse generating modules to coincide very accurately, a very high power pulse can be obtained. Such equipment is now well-established on the market in many different fields of use.
Due to the extreme demands in power and/or voltage, there are some limitations in other operational parameters. In a typical system, the pulse repetition rate ranges from 1 to 5000 Hz, while the pulse duration often is in the range of 0.5 to 20 μs. If the repetition rate is requested to be too frequent, the average power is increased and there might be difficulties. The pulse generating modules have to recover between each pulse, and such a recovery time has to be shorter than the requested time between each pulse.
The pulse generating modules are typically charged to a certain voltage during the recovery. During the pulse, typically about 10% of the energy content is released, and the voltage will drop by a smaller amount. If a next pulse is requested to have another voltage, the pulse generating modules have to be charged to this new voltage instead, i.e. they need a certain change-over time to be prepared for the new voltage. If the new voltage is higher than the remaining voltage after the last pulse, it is just a matter of having enough time to fill the energy storage. However, if the new voltage is lower than the previous one, there have to be some arrangements for lowering the voltage over the pulse generating modules. This is technically relatively complex and at the same time, a large portion of the stored energy might have to be wasted. If the output voltage is to be varied quickly, the amount of wasted stored energy may be very large indeed.
The shape of a power pulse is today typically a flat pulse with as sharp rising and falling flank as possible, respectively. Different pulse-forming arrangements are provided to achieve this appearance. In cases other pulse forms are requested, the pulse-forming networks have to be totally redesigned for each pulse shape. Furthermore, if the pulse shape also is requested to change from one pulse to another, dynamic pulse-forming networks have to be developed.